Some basic info on ecology, particularly of Palythoa caribaeorum which is abundant on some BB reefs
Taxonomy/Species ID
– Zoantharia (Cnidaria: Hexacorallia) of the Dutch Caribbean and One New Species of Parazoanthus
Javier Montenegro et al., 2020 in Diversity (Open Access)
Species of Palythoa
The Dutch Caribbean Species Register lists 8 species:
– Palythoa caracasiana
– Palythoa caribaeorum. View Photos on iNaturalist
– Palythoa grandiflora View Photos on iNaturalist
– Palythoa grandis – View Photos on iNaturalist
– Palythoa horstii
– Palythoa mammillosa
– Palythoa sp.
– Palythoa variabilis View Photo (1) on iNaturalist
– Interspecific competition between Palythoa caribaeorum and other sessile invertebrates on St. Croix Reefs, US Virgin Islands
Thomas H. Suchane & Deborah J. Green Proceedings of the Fourth International Coral Reef Symposium, Manila, 1981, Vol. 2, 679-684 ABSTRACT Palythoa caribaeorum (Duchassaing and Michelotti), an aggressive competitor for space, was observed in the field and tested in the laboratory to determine how interspecific competitive interactions may influence its abundance and distribution in a variety of reef environments. Fore-reef, reef-crest, back-reef, and patch-reef habitats were examined both for abundance patterns and for interspecific competitive battles between Palythoa and other sessile reef invertebrates. Variations in the growth rate of Palythoa were noted for invertebrates of varyingdefensive capabilities. Densities of Palythoa are affected by variability in envir onmental conditions. However, growth rates of this zoanthid are not influenced significantly by physical conditions and remain consistently high for all study sites at 2.5-4.0 mm/day. This represents one of the highest known growth rates for an anthozoan. Data also suggest that Palythoa can overgrow nearly every other sessile reef invertebrate, placing it at the top of a competitive hierarchy for reef ecosystems.
From the Introduction: Gorgonians, sponges and zoanthids are usually low in abundance, but at times may dominate up to 85% of the cover in some open reef areas, especially in shallow zones (Birkeland and Neudecker 1981, C.S. Rogers, unpubl, pers.obs.). Palythoa caribaeorum (Duchassaing and Michelotti) is an especially common zoanthid in certain shallow reef environments on St. Croix (Carpenter and Gladfelter 1979). It appears to acquire and dominate space by killing or directly hindering the growth of its competitors both by physical and chemical means. Physically, it may grow directly over the tissues of nearby corals or other invertebrates, “smothering” them (pers. obs.), but we are aware of no specific work on this interaction. Chemically, Palythoa contains a powerful high molecular weight toxin known as palytoxin (Ciereszko and Attaway, 1961, Scheuer 1964, C zko and Karns 1973, Attaway and Ciereszko 1974) which could act as an allelochemical and aid in acquiring space.
Cover Buck Island
| Zone | Avg Cover (%) | Range (%) | Depth |
| Fore-reef | 0 | 0 | to 12 m |
| Reef Crest | 36 | 6-83 | <1 m |
| Back Reef | 10 | 0-68 | 1-3 m |
| Patch Reef | 0 | 0 | 2-5 m |
– Trophic ecology of the zoanthid Palythoa caribaeorum (Cnidaria: Anthozoa) on tropical reefs
Érika Flávia Crispim de Santana et al. 2014 Journal of the Marine Biological Association of the UK 95(02):301-309 “… This species predominantly fed on diatoms, and did not take advantage of many other prey items abundant in the plankton. Our results indicate that P. caribaeorum is suspensivorous and feeds principally on small phytoplankton. As this species is prey for benthic organisms such as polychaetes and nektonic organisms, our results indicate the importance of this zoanthid in tropical reef ecosystems as a primary consumer that serves as an energy transfer link between the planktonic environment and the nektonic and benthic spheres.”
From the Intro “This species hosts zooxanthellae, symbioticdinoflagellates (Symbiodinium), in their gastrodermal tissuesthat provide the zoanthids with nutrition through transloca-tion photosynthetic products (Costa et al.,2013). Then,besides the heterotrophic source, P. caribaeorum alsoobtains photosynthetically fixed carbon from their symbioticalgae, but the real contribution of each source is stillunknown. A preliminary study of feeding in this species indicated its suspensivorous nature (Sebens, 1977), although thes mall numbers of prey encountered (N ¼34 in 610 polyps)indicated the necessity of more detailed studies.
This zoanthid species has been reported as a food item for the Bearded fireworm Hermodice carunculata (Pallas, 1766)(Suchanek & Green, 1981;Sebens,1982), the hawksbill turtleEretmochelys imbricata (Linnaeus, 1766) (Stampar et al.,2007), the banded butterfly fish Chaetodon striatus Linnaeus,1758 (Bonaldo et al.,2005) and other diverse Caribbean reeffish (Suchanek & Green, 1981). Francini-Filho & Moura(2010) suggested that P. caribaeorum was the principal food offour reef species that are, in turn, prey for large fish of commercial interest in Brazil.